An electric circuit is described in European Patent Application No. EP 1 139 442, where a plurality of series circuits having a piezoelectric element and a transistor are connected in parallel. A first measuring shunt is grounded in series with the parallel circuit. The parallel circuit is also connected, via an inductance coil, to the shared connecting point of two transistors connected to ground in series. A series circuit of a capacitor and a second measuring shunt is grounded in parallel to the two transistors.
One of the two above-mentioned transistors is provided for discharging the piezoelectric elements. For this purpose, this transistor is triggered using a clock pulse.
In the event of an error, a possibly charged piezoelectric element must be able to be rapidly discharged. An additional stop switch is provided for this case in European Patent Application No. EP 1 139 442. This is an additional transistor and an associated resistor, via which the piezoelectric elements may be discharged without clock pulse control in the event of an error. Due to the currents that may be flowing, the implementation of this stop switch requires increased complexity.